1. Field of the Invention
This invention relates to a coupling fixture to fix a coupling member, such as a gear, mainly to a shaft member.
2. Description of the Prior Art
Conventionally, this kind of coupling fixture, as shown in FIG. 12, has an outer ring and an inner ring B each having a cut and is provided at the inner peripheral surface of the outer ring A and at both axial sides thereof with tapered surfaces T1 and T2, at the outer peripheral surface of the inner ring B at both axial sides thereof with tapered surfaces T3 and T4 opposite to surfaces T1 and T2 respectively, between the outer ring and the inner ring B and at one axial side with an annular ring nut C interposed therebetween and having the inner and outer peripheries tapered surfaces T5 abutting against the tapered surfaces T1 and T3 and circumferentially continuing, between the outer ring and the inner ring B and at the other axial side with an annular washer D interposed therebetween and having tapered surfaces T6 abutting against the tapered surfaces T2 and T4 respectively and circumferentially continuing, and across the ring nut C and ring washer D with a screwbolt E for tightening them.
When the coupling fixture is used to couple a gear G with a shaft F, the outer ring A and inner ring B are interposed between the inner surface of a cutout g provided at one axial side of the inner periphery of the gear G and the outer surface of the shaft F, so that the screw bolt E is screwably tightened to move the ring nut C and ring washer D in the direction of approaching to each other, and the tapered surfaces T5 and T6 of ring nut C and ring washer urge the tapered surfaces T1 and T3 and T2 and T4 of the outer and inner rings A and B respectively, whereby the outer ring A is expanded in diameter so as to be brought into press-contact with the inner surface of the cutout g and the inner ring B is contracted in diameter to be brought into press-contact with the outer surface of the shaft F so as to integrally couple the gear G with the shaft F.
In this coupling fixture, the ring nut C and ring washer D are circumferentially continuously annular, whereby when the shaft F or the gear G has a manufacturing error, they are not rigidly coupled with each other and thus result in unstable coupling. In other words, for example, when the diameter of shaft F is smaller than a predetermind size, the screw bolt E is tightened so that an urging force caused by the ring nut C and ring washer D brings the outer ring A into rigid press-contact with the inner surface of the cutout g of the gear G. On the other hand, in spite of the fact that inner ring B is subjected to the same urging force as that applied to the ring washer C, because the shaft F is smaller in diameter the result is not to bring the inner ring B into rigid press-contact with the outer surface of the shaft F, thereby producing a difference in the urging force between the outer ring A and the inner ring b. As a result, a problem is created in that the coupling of the gear G with the shaft F by the outer and inner rings A and B becomes unstable.